This invention relates to a rust-proof sealing composition used for example in an assemblying process for vehicle bodies.
As the rust-proof sealer used for hemming portions of, for example, a bonnet, a door or a trunk lid of a vehicle, there is known in the art for example a heat curable one part epoxy adhesive.
This heat curable one part epoxy adhesive has, however, a drawback that, although it has a high adhesion strength after heat curing, it exhibits high distortion after curing, so that its coating position and volume tends to become inadequate, thus leading to distortion and lowering in quality and appearance of a component panel, which requires a corrective operation. Also, in case of using an adhesive exhibiting high curing distortion, cracks may be formed at the boundary portions between the adhesive and the steel plate due to internal stresses so that rusting tends to start at these boundary portions to lower its rust-proof properties.
Moreover, the conventional epoxy type adhesive tends to wash off easily by showering of hot water employed for example during the pre-treatment processes for electrodeposition, so that it may be lowered in viscosity and hence may be unable to perform its proper function.